l. We explored whether, and under what conditions, mechanical pulmonary ventilation can lead to ventilator-induced lung injury (VILI) at airway pressures now considered safe, i.e., airway plateau pressure of 25 cm H20. As in our previous studies (at a peak airway plateau pressure of 50 cm H20, an end inspiratory time of 2.5 s), we now show that such mechanial ventilation at a "safe" peak inspiratory pressure of 25 cm H20, and (also) at an inspiatory time of 2.5 s, will result in major functional chanes within 2 h of mechanical ventilation, with further changes during subsequent 48 - 72 h of mechanical ventilation. 2. We further explored methods to fabricate tracheal tubes coated with bactericidal agents, dispersed/dissolved in polyurethane, and evaluated their bacericidal effectiveness in long-term studies in sheep. We evaluated silver sulfadiazine (SSD) in polyurethane, and chlorhxidine (CHD) in polyurethane; and silver-platinum-carbon in polyurethane. Those coatings are highly effecive, but decrease in efficacy if thick mucus is allowed to accumulate within the tracheal tube (as is now common with sate-of-the-art suction devices). 3. To alleviate accumulation of mucus within the tracheal tube (and exend the bactericidal effect), we developed a novel system based on a modified balloon that allows rapid, and virtually total removal of all accumulated tracheal secretions, in one full sweep. The system is far more rapid and effective than conventional tacheal tube suctioning. Most importantly, there is total cleaning in just one pass, with no visible residue. 4. In sheep, using tracheal tubes coated with SSD and CHD dispersed in polyurethane see (2), and cleaned by the new system (see 3), while keeping the orientation of the tracheal tube horizontal (see 2002 annual report), we have extended the duration of mechanical ventilation, without bacterial colonization of the trachea or lungs, to 6 d; and while maintaining the tracheal tube free of all secretions, without use of systemic or topical antibiotics.